1. Field to which the Invention Relates
The invention relates to wheeled building and construction vehicles such as wheel or shovel loaders, wheel dozers, front loaders, overhead loaders, graders and the like. In this respect it more particularly is a question of building and constructional machines with pneumatic tires.
2. The Prior Art
Building and construction vehicles equipped with pneumatic tires are not normally provided with resilient suspension systems. The only cushioning means has been provided in the form of low pressure pneumatic tires. However such a cushioning effect only leads to a very small or practically negligible resilient relative displacement. In order to compensate at least to some extent for the unevenness of the ground on which construction vehicles are driven and to keep the wheels in proper engagement with the ground, four-wheel vehicles with articulated axles have been provided. Vehicles with a two-part steerable articulated chassis with the joints between the two chassis parts adapted to perform a swinging movement in a vertical plane, have also been provided.
Owing to the shortcomings of the cushioning means the speed of travel of such vehicles were confined to comparatively low limits. On uneven terrain and in the case of the use for example of wheel bearings it was hardly possible to reach speeds above 15-20 km/h. Besides this low speed limit the vehicles were uncomfortable to drive, since the jolts due to unevenness of the ground were only compensated for to a very incomplete extent by the low pressure pneumatic tires and the drivers of such vehicles were subjected to the resulting physical stresses. Owing to the comparatively low top speed of travel such construction vehicles cannot be transferred on a highway or other high-speed road to their sites of use or, if they were in fact transferred over prolonged distances substantial expenses arose. In both cases suitable low-loaders were required for transporting such vehicles.